what can i do if i cant provide my old marriage devorce certificate

Proof that your previous marriages were legally terminated is required to submit a petition for a new spouse. You will most likely get a denial or a Request for Evidence (RFE) from the Immigration Service (USCIS) if you do not provide such proof when you petition for your new spouse. If the records cannot be found, you might be able to provide secondary evidence such as a statement from the recordkeeper (Court or Records Office) stating that the records were lost or destroyed and that there is no evidence of such divorce. You may have to get other evidence such as witnesses or a statement from your previous spouse or others to show that the divorce did occur. There is no guarantee that secondary evidence will be acceptable to immigration. Seek the assistance from an attorney that can help you obtain the proof that you are no longer married to your ex-spouse.